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Microorganisms (&GM) (Fermentation and biotechnology (Fermentation:…

- - - - Yeast ferments sugar in grape juice
      - Vats: large containers which prevent air reaching wine and maintain anaerobic conditions – used in commercial wine production
      - Homemade wine: small-scale fermenters fitted with an 'airlock' – allows CO2 to escape but prevents entry of oxygen
      - Alcohol increases in concentration until yeast cells die, stopping fermentation
    - - Made from barley
      - Barley seeds germinate
      - produce amylase which breaks starch into maltose
      - maltose from seeds is fermented by yeast in a large open vat
  - - - Wheat flour and water mixed together and yeast added, forming bread dough
      - Enzymes from original cereal grains break starch into sugars
      - Sugars are respired by the yeast, extra sugar may be added
      - The yeast respires aerobically at first, producing carbon dioxide which makes the bread rise
      - The air runs out and the yeast respires anaerobically making ethanol and more CO2
      - Bread baked in the oven, expanding the gas bubbles, giving the bread a light, cellular texture, and killing yeast cells, and evaporating any ethanol from fermentation
    - - Milk that has been fermented by lactic acid bacteria
      - Milk is pasteurised at 85-95°c for 15-30 minutes, to kill any natural bacteria
      - Milk is homogenised to disperse fat globules
      - Milk cooled to 40-45°c and inoculated with a starter culture of two species of bacteria KA Lactobacillus and Streptococcus, which produce lactic acid and start to digest the milk proteins
      - Culture is kept at this temperature for several hours while the pH falls to 4.4 (optimum conditions for the bacteria)
      - The mixture coagulates as the drop in pH causes the milk proteins to denature and turn into semi-solids
      - When fermentation is finished, the yoghurt is stirred and cooled to 5°c.
      - *The drop in pH gradually reduces reproduction of lactic acid bacteria and prevents the growth of other microbes, preserving the nutrients in the milk
      - Flavourings, colourants and fruit may then be added before it is packaged for sale
  - - - water allowed to cool, small amount of sugar dissolved in the water
        –> glucose / sucrose
      - Yeast added, mixture stirred
      - small amount of water gently boiled in a boiling tube
        => removes any air dissolved in water
      - Thin layer of liquid paraffin added to the surface
        => no oxygen diffuses in from the air
      - Control apparatus set up, using dead yeast instead
      - Leave both sets of apparatus in a warm place for 1-2 hours
      - Add bung and delivery tube into lime water or hydrogen-carbonate indicator solution
      - Observations:
        
        Living yeast will produce bubbles and either turn limewater cloudy or turn hydrogen carbonate indicator from orange to yellow
        => gas is CO2
        
        Control will not bubble and nothing will change
      - Record time taken for indicator to change colour
    - - The type of sugar (eg. glucose, sucrose, maltose) affects the rate of respiration of the yeast
      - The concentration of sugar "
      - The temperature "
- - - - Another vector to introduce foreign DNA into bacterial cells
      - Attaches to the cell wall of the bacterium and injects its own DNA which becomes incorporated into the DNA of the host cell and eventually causes the production of many virus particles
- - - - Introducing a new gene or genes into plant cells
      - producing whole plants from just a few cells
    - - Cut DNA from another species with restriction enzyme to isolate desired gene
      - Isolate plasmid from Agrobacterium and cut open with restriction enzyme
      - Join cut plasmid to desired gene using ligase
      - Obtain leaf discs from plant to be modified and float on liquid containing the plasmid
        –> some will take up the plasmid
      - Cultivate leaf discs on a nutrient medium
      - Grow plantlets into whole plants whose cells now contain the foreign gene